Agree with the above, it may well have seating for four in the back but only if those seated on one side have legs.
If you are a youngster I would strongly suggest an insurance quote would be wise, infact regardless of age get a qoute first.
I reckon it's a 300tdi
We shall see if the chassis number exists with no welding in that area.
Maybe the OP can provide a photo of the chassis number stamped on the chassis.
Just so you know, if you didn't already, they never made a 1989 300tdi.
Post the advert and check it has a vin number relevant to the vehicle.
It is highly likely it will have rust, you just have to find it.
That would polish up pretty good I should think, good enough anyway.
Where would you stop though?
Once the bodywork is done, then it's the interior, then the engine etc